The forests of the Anacostia watershed play a critical role in improving water quality and stabilizing stream morphology by infiltrating rainfall, reducing soil erosion, slowing and reducing stormwater runoff, and filtering out various harmful pollutants. Forests also provide numerous other benefits, from improving air quality to creating habitat for wildlife.
Forests can be broken into categories based on their function and place in the watershed. Riparian forests are located closest to waterbodies and have the most direct impact upon water quality. Riparian forests should extend a minimum of 100 feet from the edge of the water, but riparian buffers well over 100 feet are ideal, as wider buffers provide additional water quality and wildlife habitat benefits. Within the Anacostia, approximately 60% of all streams lack an adequate riparian buffer that is at least 100 feet in width on each side. Upland forests are those forests that are located futher away from waterbodies and on tops of hills. Metropolitan Washington Council of Governments (COG) analysis results show that approximately 25% of the Anacostia watershed is covered by upland forests.
The Anacostia watershed experienced a 7.9% decline in forest cover between 1936 and 2000. This decline in forest cover was caused by shifts in land use from agriculture to residential and commercial development. Using 1936 and 1938 black and white aerial photographs, COG staff has identified forest stands that are likely to be at least 65 years old, and therefore considered mature. Mature hardwood forest makes up about half of the total forest coverage in the Anacostia watershed.